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std: GeneralPurposeAllocator: set freed bytes to undefined

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Helps catch use-after-free. Caught a couple issues in the self-hosted
compiler.
This commit is contained in:
Andrew Kelley 2020-08-25 13:36:40 -07:00
parent ea6a076065
commit 6fb105fdd7
1 changed files with 4 additions and 2 deletions
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6
lib/std/heap/general_purpose_allocator.zig
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@ -433,8 +433,7 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
const bucket_slice = @ptrCast([*]align(@alignOf(BucketHeader)) u8, bucket)[0..bucket_size];
self.backing_allocator.free(bucket_slice);
} else {
// TODO Set the slot data to undefined.
// Related: https://github.com/ziglang/zig/issues/4298
@memset(bucket.page + slot_index * size_class, undefined, size_class);
}
}
@ -567,6 +566,9 @@ pub fn GeneralPurposeAllocator(comptime config: Config) type {
const new_aligned_size = math.max(new_size, old_align);
const new_size_class = math.ceilPowerOfTwoAssert(usize, new_aligned_size);
if (new_size_class <= size_class) {
if (old_mem.len > new_size) {
@memset(old_mem.ptr + new_size, undefined, old_mem.len - new_size);
}
return new_size;
}
return error.OutOfMemory;